Let
L=6t+5
W=2t+1
so
Part A
Remmber that
The perimete is given by the formula
P=2(L+W)
substitute given vales
P=2[(6t+5)+(2t+1)]
P=2[8t+6]
P=16t+12
The answer Part A is
P(t)=16t+12
Part B
The area of the rectangle is given by the formula
A=L*W
substitute given values
A=[(6t+5)*(2t+1)
Apply distributive propety
A=12t^2+6t+10t+5
A=12t^2+16t+5
the answer Part B is
A(t)=12t^2+16t+5